How to go about tidying battery connections

[electric_nan]

Got a 30 year old motorhome that over the years previous owners have added their own adhoc wiring to the leisure battery, on top of the factory fitted connections, and needs a tidy up before I go and add a solar panel. Over the weekend I diagnosed the connections as:

 

1) From the motorhome control panel (factory fitted - runs under the chassis)

2) Split charge relay (factory fitted - runs under the chassis)

3) Inverter (prev owner - runs through the cab)

4) Dashboard 12v socket (prev owner - runs through the cab)

5) Kitchen 12v sockets, usb and voltage reader unit (prev owner - runs through the cab)

 

It's quite a mess already without me adding a solar connection. My plan is to add a 6-way fuse box (100 amps total, allowing for any possible future additions) behind the drivers seat for the inverter, dash socket and kitchen sockets, requiring a 40mm2 wire to the engine bay where the battery is (about 2.5 meters cable run) getting the total connections down from 6 to 4.

 

Problem is, it still seems like a large number of connections. Any suggestions on tidying this up further? Is there a way to combine these connections into 1? Still learning this stuff so any help appreciated.

 

Thanks

[pepe63xnotuse]

Hi

Is there not such a thing as battery terminal clamps that have a row of studs,so that at least each cable could be attached in a neat(er) row?

 

[spirou]

Tidy up by using bus bars

https://www.amazon.com/Electrical-Bus-Bar/s?k=Electrical+Bus+Bar

 

[Derek Uzzell]

pepe63 - 2020-04-29 8:06 PM

 

Hi

Is there not such a thing as battery terminal clamps that have a row of studs,so that at least each cable could be attached in a neat(er) row?

 

It is certainly possible to obtain battery terminal clamps with three ‘studs’

 

https://www.12voltplanet.co.uk/battery-terminal-clamps.html

 

but I’m not sure if clamps with a greater number are available.

 

It might make sense to fit to the battery’s positive terminal a 3-stud clamp to which the control-panel and split-charge relay cables are connected, with a 3rd cable being taken into the cab for the inverter and dashboard/kitchen sockets. Within the cab that cable could connect to a bus-bar (as spirou suggests) or to a fused distribution block.

 

Multi-way fused distribution blocks are widely advertised (6-way example here)

 

https://www.ebay.co.uk/c/14028099462

 

but if high amperages are involved it would be necessary to ensure the product could cope.

[electric_nan]

Bus bar seems like a good route to take.

 

What I'm thinking then, as you should fuse as close to the battery as possible , is putting two seperate bus bars in the cab: 1) for the control unit and split charge 2) for the fuse block and solar controller from the cab, with the fuses on the load end of the bus bar so I can still disconnect individual circuits as and when needed. The two seperate block will then feed into a dual terminal clamp.

 

How does that sound?

[electric_nan]

Been mulling over this and now that I think about it, are there any drawbacks to hooking up the charge controller directly the aux fuse box, as long as the wires are adequately sized etc. allowing for only one cable running from the cab to the battery. The charge controller will only be 20 amp so will only require a 20amp fuse. I know most schematics like to seperate the load from the charge side, but do the electrons actually care?

 

Think I'd rather spend my money on a solid fuse block and one thick cable run if possible, certainly tidier.

[pepe63xnotuse]

Mornin'..

 

I can see the sense in tidying and re-routing any previous owner add-on, and maybe taking them to the one, easy to get at fuse/distribution unit (one that you can "feed to" your bits'n'pieces)..but as for any main, original equipment feeds, I think I'd just leave them at the vehicle battery.

 

Okay, I'd perhaps tidy them up (by using multi stud battery clamp or nearby mounted "bus bar" ?) but what's really going to be achieved by dragging out the OE cabling?

 

( I am not an electrician..so the forum's electrickery-scientists may well say different ) :-D

[electric_nan]

I'm not planning on rerouting the original wiring from under the chassis, unless perhabs a bus bar so I can use a dual clamp on the terminal, with a fuse block for the add ons inside the cab going to the other connection in the dual clamp, does that make sense?

[electric_nan]

I was thinking something like this inside the cab for the ktichen DC, dash socket, inverter and solar controller:

 

https://www.bluesea.com/products/5024/ST_Blade_Battery_Terminal_Mount_Fuse_Block_Kit

 

Then feeding the thickest cable I can afford from there to the battery (about 2.5 meters) with a 125 amp fuse inbetween (closest to the battery), and a thinner negative cable running to the chassis inside the cab.

 

Then a dual bus bar for the factory fitted circuits inside the cab (circuit board and relay), then a single thicker cable with a fuse to the remaining terminal clamp connection.

 

How does that sound?

[spirou]

Just a suggestion from my own experience... Draw a diagram of how things are wired now and how you want it to be because it's hard for others to have the same big picture view of the system based on descriptions alone. It might be crystal clear to you, as you've been looking at it for days, but even photos are sometimes too confusing.

[pepe63xnotuse]

Yes, being honest Lew(the OP) has started to lose me with that last post? :-D

 

I thought it was "just" a case of running suitable cables to an additional, "accessory" fuse box- to take the "add-ons" that currently feed from the battery and the solar stuff- and then just tidying up the remaining OE wires that were left at the battery?

 

The mention of a "...dual bus bar for the factory fitted circuits inside the cab (circuit board and relay),....." etc has lost me?(not difficult)

Is this base vehicle stuff or hab' conversion stuff?

Either way, I thought it was only the "add-ons" that were being majorly messed with?

 

If (IF?)the "..factory fitted...circuit board and relay.." that is now being mentioned is the main board/unit for the conversion side, is there any merit in looking at upgrading that for a unit that has the capability to receive all of the wires that you are looking to accommodate?.

(Personally I'd leave the OE stuff alone though..If it isn't broke, don't try to fix it .. ) :-D

[electric_nan]

I'll try to draw up a diagram later, but will try to clarify...

 

As it stands right now:

 

1) The factory fitted wiring (2 cables) includes the control panel - which is being fed from the back of the motorhome, under the chassis and through to the engine bay - and the relay - which sits inside the engine bay.

2) The additional wiring (3 cables) is coming through the cab, this is for the inverter, dash docket and kitchen sockets.

 

I plan to install a solar panel that will require a 20amp controller, which will add another connection to the battery from the cab, totalling 4 from the cab and 6 to the battery. The connections are already a mess and hard to follow, so the plan is to tidy and reduce these connections. So my plan thus far is:

 

1) A 100amp fuse box that sits behind the driver's seat for all 4 of the non-factory fitted wiring - inverter, dash socket, kitchen sockets and solar controller.

2) Connect the fuse box to the battery with the appropriate sized cable (40-50mm2 over 2.5 meters) and fuse near the battery (125 amps)

3) Ground this fuse box to the inside chassis.

4) Then connect the two cables from the control panel and relay to a bus bar, combining them and allowing me to reduce the total connections to the terminal to 2 - unsure on this, might not be worth it as 3-way terminal clamps are easy to find, but dual clamps look tidier.

 

Hope that clears things up?

[Derek Uzzell]

The stated objective is to tidy and rationalise the cables that are currently connected to the under-bonnet leisure-battery, plus keeping in mind that the addition of a solar panel system is planned.

 

I would have thought that - as the cable connections at the battery’s positive terminal are a mess - it’s likely that this is also the case at the battery’s negative terminal. So if the live cabling is to be tidied, it would make sense to do the same with the earth cables.

 

I don’t see it as a particularly difficult task to produce a much neater under-bonnet cabling solution and to relocate some of the present cables into the cab area where they can be fuse-protected and grouped together. But how I’d go about the task would undoubtedly differ from how Spirou would do it and there’s every reason to think both approaches would be effective.

 

Lew’s latest plan seems similar to what I was suggesting in my posting of 30 April 2020 7:53 AM above.

 

(I certainly agree with Spirou that drawing ‘before and after’ wiring diagrams should be done to concentrate the mind.)

[electric_nan]

Thanks Derek. I've tried to clarify a little more clearly above your comment, but yes, much like your original plan.

 

The ground connections aren't too bad actually as it looks like the negatives from the individual components are being connected to the chassis, not the battery itself. The negative terminal of the leisure battery has a killswitch on it and then connects to the chassis (from what I can remember). It's definitely not as bad.

[electric_nan]

Fag packet sketch #1 (current wiring):

[electric_nan]

Fag packet sketch #2 (proposal #1):

[spirou]

Much clearer B-) if it's feasible then I quite like the idea of a single, large cross section cable replacing previous ones. But, bear in mind a thick cable might be difficult to route through tight turns and is generally not easy to work with and crimp.

 

Also, you can consider a splitter fuse box often sold as car audio equipment as it serves the combined role of bus bar and fusing.

 

First example i found, though perhaps not ideal with the useless display

https://m.ebay.com/itm/Distribution-Block-1x0-In-2x4GA-Out-Splitter-Fuse-Box-for-Car-Audio-Marine-US-/372864252105

[electric_nan]

I'll bare the splitter fuses box idea in mind, thanks.

 

I assume the solar controller going into the fuse block is fine then I take it?

[spirou]

Sure, you'd want a fuse on the output from the controller, possibly on the input as well as it makes it easier to disconnect for maintenance.

 

However, an additional note... ideally any charging source should be wired as close as possible to the battery. The solar controller would ideally not be further away than 50cm or so, and you'd have the longer run from the panels to the controller to mitigate voltage drop.

[electric_nan]

I'm planning on using a 20 amp double pole switch, as mentioned here https://goingnomad.co.uk/installing-a-solar-panel-on-a-motorhome/, as soon as the solar panel cables reach inside, this being where the motorhome control panel and trip switches are towards the back of the van, then running the rest of the length of cable to the front where the controller will be connected to the planned fuse box at 20amps (about 2.5 meters away from the battery). According to an online wire size calculators, at that distance and rating (100 amps) I can get away with a 35mm2 wire whiile only losing 2% (0.24v). Can't imagine that being a big deal, unless anyone more knowledgable than me thinks otherwise.

[Airstream]

How about

https://www.autoelectricsupplies.co.uk/mobile/product/1100/category/63

Ray

[spirou]

0,2V might not sound much, but remember you're dealing with quite a narrow range. A standard lead battery SOC operating range is somewhere between 12.6 and 11.8. On the other side you might have a charger that uses 14.2V as absorption and 13.8 as float voltage. Being 0.2V off is not so small relative to that range. It helps if those parameters can be adjusted, as with Victron and possibly some other brands.

 

It's not the end of the world by any means, there are far worse cases. In the previous van I had about 4m of 2x6mm2 to the battery. Just saying you should consider possible alternatives of where to place the controller.

[electric_nan]

The problem I have is I can't get the controller any closer to the battery unless I either moved the battery under the passengers seat, which would require rerouting the original connections from the relay and control panel, and don't think the battery would fit anyway, or place the controller inside the engine bay, which won't fit and doesn't sound practical in a dirty, outside environment.

 

I was thinking using something like this would help counteract these issues:

 

https://www.renogy.com/battery-voltage-sensor-with-battery-ring-terminals/

 

In which case, could I afford an even greater loss of voltage on the wire as the usual recommended loss is between 3-4%? For example, 25mm2 would only give me 2.83% loss.

[Derek Uzzell]

electric_nan - 2020-04-30 5:24 PM

 

Fag packet sketch #2 (proposal #1):

 

Introducing a bus-bar into the cabling that connects to the starter-battery and control-panel adds another component (the bus-bar) and another fuse.

 

At present, if either of the two fuses in your first sketch fails, it’s likely that the other fuse will not have failed. With your proposed change, if the fuse between the leisure-battery and bus-bar fails, the links to the starter-battery and control-panel will both be affected.

 

Your proposal still has two cables connecting to the leisure-battery’s positive terminal, so it seems to me that - by utilising a 3-stud battery-terminal clamp - you can retain the present straightforward separate fused cabling to the starter-battery and control-panel and dispense with the additional bus-bar and fuse.

 

There comes a point where being tidy stops and obsessing over tidiness starts ;-)

[electric_nan]

Yup, I agree. Getting carried away thinking of all the possibilities is an entertaining exercise.